Background: Pemetrexed monotherapy has come to be recognized as one of the standard secondline therapies for advanced nonsquamous nonsmall cell lung cancer (NSCLC). However, there have been no reports of studies that have evaluated the efficacy of pemetrexed according to type of active EGFR mutation, i.e., an exon 19 deletion or an L858R point mutation. Materials and Methods: The records of nonsquamous NSCLC patients harboring an EGFR mutation who received pemetrexed monotherapy as a second or later line of chemotherapy at Kitasato University Hospital between March 2010 and October 2015 were retrospectively reviewed, and the treatment outcomes were evaluated. Results: The overall response rate and progressionfree survival time (PFS) of the 53 patients with nonsquamous NSCLC were 15.1% and 2.3 months, respectively. There were significant differences between the disease control rate (37.5% vs. 76.2%) and PFS time (1.8 months vs. 3.3 months) of the exon 19 deletion group and the L858R point mutation group, and a multivariate analysis identified type of EGFR mutation as well as performance status (PS) as independent predictors of PFS. Conclusions: The clinical data obtained in this study provided a valuable rationale for considering type of EGFR mutation as well as non squamous histology as predictors of the efficacy of pemetrexed monotherapy.